body{
    background: url("/images/login.jpg") no-repeat center 0px;
    background-position: center 0;
    background-size: cover;
}
.main{
    text-align: center; /*让div内部文字居中*/
    background-color: #fff;
    background-image: url("/images/诗花月.jpg");
    border-radius: 20px;
    width: 300px;
    height: 350px;
    margin: auto;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
}

